Dynamic Division size

[Jezternz]

Hey,
there is something I have wanted to know for a while, but I have never been sure whether it is possible in html/css.
Basicly I want to have 3 divisions.
html eg:

<div id="top">a</div>
<div id="mid">b</div>
<div id="bottom">c</div>
 

and what I want to do is have is to have divisions "top" and "bottom" to have constant heights and the mid div to just cover the rest of the height of the page, I was wondering if this was possible in css/html without the need of javascript?
(Also I am looking to avoid tables if possible).
css eg:

#top{width:100%;height:50px;}
#mid{width:100%;height:????;}
#bottom{width:100%;height:150px;}
 

thanks, Josh

[drhowarddrfine]

Do you mean you want the top want to stay at the top and the bottom one to stay at the bottom like this?

[Jezternz]

well yes, but I could just use absolute positioning for that, the more important thing is that the central division resizes itself, to fit the spare area, when the window is resized.